Discourse from a general standpoint is the capacity of orderly thought or procedure. In conversation, it is the orderly flow of ideas wherein certain topics are introduced and grouped in organized manners, and additional information expands on these topics by saying something about them. One example of a discourse is a book wherein the lowest level of a topic exists in sentences. Generally, a sentence is a grammatically self-contained language unit consisting of a word or a syntactically related group of words that express an assertion, a question, a command, a wish, or an exclamation; that in writing usually begins with a capital letter and concludes with appropriate ending punctuation; and that in speaking is phonetically distinguished by various patterns of stress, pitch and pause. Each sentence in a discourse can be said to have a topic, explicitly stated or implied, and a focus, or something that is being said about the topic.
In general, theme identifies which topic is really being discussed and what is being said about that topic. To understand the thematic information in a sentence, an analysis method is needed that is able to experience all of the subtle nuances that a writer conveys to a reader in less tangible ways. The human mind does not understand information by analyzing the grammatical content of a sentence. Many sentences are identical in grammatical context but are very different because of the specific selection of words and what additional facets of understanding the words add to the understanding of the sentence. The difference does not just influence the topics by introducing another different idea, but also influences the level of importance that each word has in the sentence by indicating new, extra-grammatical, thematic contexts. Therefore, prior art systems that determine the importance of theme by counting the number of times words appear in a document do not accurately determine theme.